Rotary shaft seals have been used in machinery, the automotive industry, as well as other industries. For example, such applications can include use on transmissions, pinions, gears, axles, etc. that require a symmetrical functioning dynamic seal (i.e., the seal must function effectively in both directions of shaft rotation). The seal has an air side and a lubricant side. The seal helps maintain the lubricant (e.g. oil) on the lubricant side. Lubricant may, however, leak from a lubricated side to the non-lubricated (air) side through the interaction of the active surface of the seal with the shaft. Spiral grooves or built-up ribs (hereinafter collectively referred to as grooves) disposed on the active side of the seal capture the leaked lubricant and hydrodynamically pump the lubricant back into the lubricated side due to relative rotation between the seal and the shaft about which the seal is disposed.
Typically, the grooves are arranged in a spiral or helical configuration on the shaft-contacting side of the seal. In order to enable hydrodynamic pumping of captured lubricant, the grooves spiral along the active surface of the seal in opposite directions to accommodate relative rotation between the shaft and the seal regardless of the direction of the relative rotation. The grooves are open at the lubricant side of the seal and communicate with the lubricant therein. Having the grooves open at the lubricant side of the seal creates potential problems. For example, static oil leaks can develop. Additionally, air leakage during pressurization testing of the machinery on which the seal is being used at the end of the assembly stage can also occur. Accordingly, it would be advantageous to provide a dynamic seal having a bi-directional pattern thereon to capture lubricant that leaks past the seal edge and returns the same to lubricant side of the seal. Furthermore, it would be advantageous if such a dynamic seal minimized and/or avoided the drawbacks mentioned above.
A dynamic seal according to the principles of the present invention advantageously provides for the return of captured lubricant to the lubricant side regardless of the direction of the relative rotation between the seal and the shaft. The seal uses symmetrical pumping elements to facilitate the hydrodynamic pumping of the captured lubricant in response to the relative rotation. The symmetrical pumping elements have ending points that stop short of the seal edge of the seal. The seal may utilize secondary pumping elements that communicate with the primary pumping elements to capture lubricant that is not captured by the primary pumping elements. The secondary stage pumping elements capture the excess lubricant and deliver and transfer the lubricant to the primary stage pumping elements for subsequent hydrodynamic pumping back into the lubricant side of the seal.
In one aspect of the present invention, a bi-directional dynamic seal includes a lubricant side and a non-lubricant side. There is a sealing portion having an active surface that communicates with the non-lubricant side and a seal lip at an end thereof. The seal lip faces the lubricant side. The seal lip defines an opening in which a shaft can be disposed. The active surface is operable to engage with and seal against a shaft disposed in the opening. A plurality of pumping elements extends along the active surface. The pumping elements stop short of the seal lip and there is a static dam therebetween. The pumping elements are operable to capture lubricant that leaks past the seal lip and pump the captured lubricant toward the seal lip, past the static dam and back into the lubricant side due to relative rotation between the active surface and the shaft disposed in the opening. The pumping occurs regardless of a direction of the relative rotation.
In another aspect of the present invention, a dynamic bi-directional seal includes an active surface operable to engage with and form a seal against a shaft. There is a seal lip that defines an opening which is operable to receive a shaft. A bi-directional fluid pumping pattern is located on the active surface and is operable to capture lubricant that leaks past the seal lip and pump captured lubricant to a lubricant side. The pumping pattern includes a plurality of primary pumping elements that extend along the active surface. Each primary pumping element has a pair of termination points adjacent the seal lip. Each primary pumping element also has an induction point remote from the seal lip. The pumping pattern also includes a plurality of secondary pumping elements extending along the active surface. The primary pumping elements are disposed between the secondary pumping elements and the seal lip. The secondary pumping elements are operable to capture lubricant that leaks past the primary pumping elements and direct captured lubricant to the induction points of the primary pumping elements.
In yet another aspect of the present invention, a method of returning lubricant that leaks past a seal edge of a seal on a shaft back to the lubricant side of the seal is disclosed. The method includes (1) capturing lubricant that leaks past the seal edge with a plurality of primary pumping elements on an active surface of the seal; (2) capturing lubricant that leaks past the primary pumping elements with a plurality of secondary pumping elements on the active surface of the seal, the primary pumping elements being disposed between the seal edge and the secondary pumping elements; (3) transferring lubricant captured in the secondary pumping elements to induction points of the primary pumping elements; and (4) pumping lubricant captured by and/or transferred to the primary pumping elements to the lubricant side of the seal with relative rotation between the active surface of the seal and the shaft regardless of a direction of the relative rotation.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.